(GH-77) Push to gallery on new tags

Instead of pushing on merges to master, push to the PowerShell gallery
on new tags being added. We want to use tagging for versioning and
getting to version history in the repository, so it's good to just set
that up appropriately.

AppVeyor/AppVeyorDeploy.ps1

@@ -18,7 +18,7 @@ Write-Host "Updating module manifest to version: $env:APPVEYOR_BUILD_VERSION"
 # Publish to PS Gallery           #
 #---------------------------------#
 
-if ( ($env:APPVEYOR_REPO_NAME -notmatch 'chocolatey') -or ($env:APPVEYOR_REPO_BRANCH -notmatch 'master') )
+if ( ($env:APPVEYOR_REPO_NAME -notmatch 'chocolatey') -or (!$env:APPVEYOR_REPO_TAG_NAME) )
 {
     Write-Host "Finished testing of branch: $env:APPVEYOR_REPO_BRANCH - Exiting"
     exit;

readme.md

@@ -38,7 +38,7 @@ Here's the general process of fixing an issue in the DSC Resource Kit:
 Build and Publishing
 ============================
 
-AppVeyor is used to package up the resource and publish to the Powershell Gallery (on successful build from master branch only). 
+AppVeyor is used to package up the resource and publish to the Powershell Gallery (on successful build from a newly pushed tag only).
 
 The AppVeyor scripts do the following:
 - Test the resources using 'xDSCResourceDesigner'